Our client went to a local hospital for a shoulder replacement surgery. The anesthesia for the procedure was provided by a certified registered nurse anesthetist (CRNA), rather than an anesthesiologist physician. The CRNA chose to use a type of anesthesia called an interscalene nerve block.

An interscalene nerve block is a type of local anesthesia, as opposed to general anesthesia, where the patient is put to sleep during the surgery. It involves administering anesthetic medication to the roots of the bundle of nerves in the armpit area called the brachial plexus. This type of nerve block gets its name because the C5 and C6 nerve roots pass between the anterior and middle scalene muscles.

When she awoke from surgery, she immediately noticed that she had trouble breathing and told the healthcare providers. They advised her that it would get better. Her problems breathing got so bad that her physical therapist stopped a session to call her doctor.

The doctor ordered a hemidiaphragm evaluation, which found that her diaphragm was stuck in the up position, causing her lung to be pushed up. Other vital organs had moved into the place where the lung belonged. This should not have happened if the anesthesia provider—a CRNA, not an anesthesiologist physician—had been monitoring her appropriately during surgery.

Phrenic nerve palsy

Interscalene brachial plexus block is the most common regional anesthetic technique used in shoulder surgery. An important risk of using this form of anesthesia, though, is phrenic nerve palsy and paralysis of the diaphragm.

The phrenic nerve originates mainly from the C3, C4, and C5 nerve roots and then passes down between the lung and heart to reach the diaphragm. The diaphragm is the muscle that separates the chest and abdominal cavities. It is the main muscle of respiration that aids in expansion of the lungs, accounting for 75% of the increase in lung volume when breathing in. The phrenic nerve’s important function is to control the movement of the diaphragm.

In almost every case where an interscalene block is used as the anesthetic root in shoulder surgery, patients wake up with temporary, or transient, phrenic nerve palsy. For most people, though, it quickly goes away.

Certain patients are at a higher risk, though, for persistent (long-lasting) phrenic nerve palsy. These high-risk patients include those with pulmonary disease, obesity, or obstructive sleep apnea. Without treatment, persistent phrenic nerve palsy can become permanent and very disabling.

Causes of persistent phrenic nerve palsy

The medical literature reflects several different causes of persistent phrenic nerve palsy. One cause is nerve damage from direct needle trauma or an injection of anesthetic into the nerve itself. This risk can be minimized with an ultrasound-guided technique, rather than having the anesthesia provider use anatomical landmarks. Other causes include inflammatory scarring causing nerve entrapment, double crush syndrome (pre-existing cervical spine stenosis is aggravated by the anesthesia), and triple crush syndrome (ischemia, or reduced blood flow caused by high volume of local anesthetic).

Paralysis of the diaphragm

When the phrenic nerve is damaged, the major victim is the diaphragm. Fortunately, damage to the phrenic nerve on one side will only impair the diaphragm’s function on that same side. Losing half of the diaphragm’s function, though, makes it hard to breathe and function.

Standards for safe interscalene nerve blocks

Considering that the risk of phrenic nerve palsy is well-known in shoulder surgery, the standard of care requires the anesthesia provider to limit the amount of anesthetic injected. Studies have shown that there is a direct relationship between the anesthetic volume injected and phrenic nerve palsy. Experts have concluded that an injection around the C5-C6 nerve roots of greater than 20 mL inevitably produces phrenic nerve palsy.

When using an ultrasound-guided technique, injecting only 5-10 mL of anesthetic medication has a dramatic reduction in the incidence of phrenic nerve palsy, without compromising the desired pain control for up to 24 hours after the surgery.

The medical literature also supports reducing the local anesthetic concentration, using ultrasound guidance to inject out of a precise site (called the periplexus), injecting farther away from the C5-C6 nerve roots.

We are here to help

If you or a loved one has been seriously injured because of medical malpractice, call Painter Law Firm, in Houston, Texas, at 281-580-8800, for a free consultation about your potential case.

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Robert Painter is an attorney at Painter Law Firm PLLC, in Houston, Texas. He is a former hospital administrator who files lawsuits on behalf of patients and family members against hospitals, anesthesiologists and nurse anesthetists, surgeons, and other healthcare providers. In 2017, H Texas magazine recognized him as one of Houston’s top lawyers.